If you want to do it properly, you would remove everything from the board in that general area and clean it manually. It'll make the necessary repairs to the tracks easier.

Or you just keep soaking it in acid until it dissolves it all and hope it doesn't eat too much actual copper.

Thanks for replying. That will give me more practice for sure, I'll take multiple pics of the components to be sure.
I noticed that some of the traces on the mask were gold, that means that the mask is gone not that the trace is gone, right?
When you say manually clean it, how would I do that? With a polish tool on my dremel and try and be gentle?

Looking for as much detail as you guys are willing to throw at me, I really want to learn. I've been watching Youtube videos for months...
But this retired brain isn't as sharp as it once was (if it ever was!!)
Joe

Oh, one more thing about dissolving the green stuff - the vinegar doesn't cause ANY bubbles or fizzing at all.
Neither does the baking soda.

I'd use a toothbrush and soap.

Just because something looks gold doesn't mean it's literally gold.

You won't really know anything useful until you've cleaned it, inspected thoroughly, and probed the tracks for continuity.

The good thing is the traces are nice and wide and easily visible.

At an absolute minimum you need to remove the keyboard socket and the keyboard controller IC and socket from the board - you may still have to remove the smaller components, but start with those. They are big, easy places for that nasty corrosion to hide, and if you don't get it all it will continue eating its way through the board.

Toothbrush and vinegar/soap/IPA to start. Then possibly an abrasive like a fibreglass pencil for more stubborn areas, or areas you need to clean the mask off in order to get a better surface to start from.

The green is oxidised copper, it'll always come back.

What I do is use solder + flux + copper wick/braid, and move the wick over the surface to coat it evenly. If you want it non-conductive you can use liquid solder mask on top.

Well, I gave it a go. I managed to get the worst components off but the blue caps were awful! One was just about glued down by corrosion.
I tried really hard to go slow and careful, but it looks like on the back side of the board that one of the caps the pads aren't shiny anymore.
Does that mean I'm out of luck now? I tried to give the whole area a nice dose of flux and reflow of solder, but as you can see, that's what I have now.
Chalk it up to a learning experience and move on to the next project?
I'd love to continue to fix it if at all possible... but I know my novice soldering/unsoldering skills may have done me in!

Thanks for all the kind replies!
Let me know how best to proceed or not to!
Joe

WARNING L……

Do NOT Deep soak the Motherboard in Vinigar and water solution
It will eat away at components and destroy your motherboard.
Just clean each corroded section with vinigar and water solution and wash with water after 5 or 10 minutes.

Then you can wash the entire motherboard in disk liquid soapy water and rinse with clean water
Blow dry with Air compressor and let dry for 1 day in Mild sun light NOT full sun light
Full Sun light might melt or damage the board.and components

You may try a little ammonia over the green corroded traces, it dissolves copper compounds quite well. Don't let it sit there too much, only a few minutes then wipe it away, wash first with water then apply a little vinegar again and then once more water. It will not fix anything but will remove the green copper crust. You will know it's working if the green turns a deep blue and dissolves away. What you hope to achieve with this is to remove the corrosion and have a better look at what's left beneath.

Another way to do it is to use one of those solutions they sell for cleaning silver jewelry, they contain thiourea which is also good for dissolving silver and copper compounds.

(edit) here's an example of the latter. Just apply a few drops with a pipette.

Rationale: if the corrosion is caused by chloride ions (for instance if the board was exposed to salt water etc) then vinegar will not work for cleaning, but the 2 methods above likely will work. There's a term in numismatics used for this, it's called "copper disease" or "bronze disease" because it affects old coins made of copper or bronze. There are other, milder ways to get rid of it (sodium sesquicarbonate is one) but they take weeks or even months for results, you don't want to be soaking the motherboard for that long in chemicals. 😀